调控DNMT上调SERCA2a表达纠正脓毒症心肌病的研究

Sepsis induced cardiomyopathy (SIC) has a significant influence in the fate of patients with sepsis. The presence of SIC in sepsis is associated with a significantly increased mortality rate of 50% in septic patients. The decreased expression of the cardiac sarcoplasmic endoplasmic reticulum Ca2+ ATPase (SERCA2a) has been widely found in SIC and how to restore SERCA2a’s expression in sepsis receives a lot of attention. DNA methylation is a process regulated by DNA methyltransferase (DNMT), in which the methyl groups are added to DNA and modifies the gene transcription without changing the sequence of DNA. When located in a gene promoter, DNA methylation typically acts to repress gene transcription. Previous studies have found that the SERCA2a expression was modulated by the status of DNA methylation. Based on it, we carry on the project which is aimed to determine whether enhancing SERCA2a expression by regulating DNMT can protect heart against sepsis. The answers will be helpful in understanding the etiology of SIC and cue a novel way in correcting SIC in clinic.

脓毒症心肌病（SIC）显著影响脓毒症预后。合并SIC的脓毒症患者，死亡率高达50%。心肌肌浆网钙三磷酸腺苷酶（SERCA2a）表达下调在SIC中普遍存在。恢复受抑制的SERCA2a表达是目前的研究热点。DNA甲基转移酶（DNMT）通过调控DNA甲基化，改变局部DNA空间结构，在不改变DNA序列的情况下调控基因表达。既往研究发现：SERCA2a表达受DNA甲基化调控。在此基础上，本项目拟进一步研究调控DNMT上调SERCA2a表达是否能纠正SIC，同时探讨其分子机制。研究结果将有益于对SIC病理生理机制的认识，同时为临床上处理SIC提供新的思路。

败血症心肌病（sepsis induced cardiomyopathy，SIC）通常伴有肌浆网钙三磷酸腺苷酶2a（sarcoplasmic reticulum Ca2+-ATPase 2a,SERCA2a）表达下调和功能受损，如何提高SERCA2a表达和功能是纠正败血症心肌病的重要策略之一。我们前期的研究发现DNA甲基化异常可能在SERCA2a表达调控中发挥关键作用。本项目旨在考察其内在的分子机制。首先我们明确了SERCA2a表达水平与SIC时心脏功能下降呈负相关，提高SERCA2a表达有助于纠正SIC时的心脏功能下降。进一步我们在体外和体内模型考察DNA甲基化异常在SERCA2a表达调控中的作用，在盲肠穿刺结扎构建的小鼠SIC模型中，给予DNA甲基化抑制剂干预能减轻SIC时的SERCA2a表达下降和心功能损害，也能明显改善SIC时表达上调的DNA甲基转移酶1（DNA methyltransferase 1, DNMT1）。在体外试验中，用脂多糖（lipopolysaccharides, LPS）处理心肌细胞建立模型，DNA甲基化抑制剂也能减轻LPS引起的SERCA2a表达下降和心肌细胞收缩功能损害。.我们进一步探索了SIC时DNA甲基化增加的机制。SIC时，心肌细胞缺氧，缺氧诱导因子1α（hypoxia induced factor 1α，HIF-1α）表达上调，它作为转录因子能够上调DNMT1的表达。体内实验中，对心肌特异性HIF-1α敲除能减轻SIC心脏损害，DNA甲基化异常和SERCA2a的表达下降。细胞试验中，HIF-1α失活能减轻LPS导致的心肌机械功能异常。